Have you ever believed in something so strongly that you made it real?

William Joyce definitely has.

The artist and storyteller, who wrote the books Dinosaur Bob and George Shrinks and did character design for the movies Toy Story and Robots, wanted his daughter, Mary Katherine, and son, Jack, to have no shadow of doubt that Santa Claus, the Easter Bunny, and the Tooth Fairy were real. So he began planting evidence – like a bad cop, or maybe the world’s best dad.

Those efforts have led to a series of books and an upcoming 3-D film from DreamWorks Animation, Rise of the Guardians, in which tough-as-nails versions of childhood icons join forces to combat a Boogeyman named Pitch.

With a new trailer showing off the Nov. 21 movie, Joyce takes a deep dive with EW on the story behind his backstories.

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The way Joyce explained it to his own kids, the more faith one has in the existence of what he dubbed The Guardians of Childhood, the more power these protectors have.

Unusual footprints appeared around the house on holidays, a trail of glitter might lead from a pillow to an open window, and in addition to physical evidence, Joyce began creating elaborate backstories for these characters. “Spider-Man had one, why not Santa?” he says.

It all began when his daughter was born nearly 20 years ago. “It was like, ‘Yay, I can tell my kids about these characters!’” Joyce says. “Then I realized: I don’t know much. The mythologies presented to me were very very vague. Some of them seemed to be fading away a bit, like the Sandman, whose story seemed to be missing. I thought, ‘This is bad.’”

The author and artist also had another notion: “I thought, ‘This is what I do!’ I’m going to get into this and roll up my sleeves and discover a mythology.” As he set about telling his children his own histories for the Man in the Moon, Santa, the Easter Bunny, the Tooth Fairy, and the Sandman, his daughter helped bring it all together.

“It was a question from her early on: Do they know each other?” Joyce recalls. “And I thought, YEAH. They KNOW each other.”

It’s a happy memory for the artist, though his family later had more than their share of painful ones. Mary Katherine lost her life two years ago from a brain tumor, at age 18. Her name has adorned seemingly everything Joyce has created since, from his Guardians of Childhood books, to his recent Oscar-winning animated short, The Fantastic Flying Books of Mr. Morris Lessmore, the first big project of his Shreveport-based Moonbot Studios.

Like any great muse, her influence transcends the hardships real life has to offer, and the stories she and her brother helped inspire are being shared with the rest of the world, with the books beginning publication last fall, and the movie hitting theaters next fall.

Our collective view of Santa Claus has been shaped by everything from Gene Autry’s recording of Rudolph the Red-Nosed Reindeer to Clement Clarke Moore’s poem A Visit from St. Nicholas(later to be known as T’was the Night Before Christmas. Even Coca-Cola ads helped popularize the red suit and white trimming, though the company didn’t invent that look, as many think. (Hey, belief makes things true, right?)

“And with the Easter Bunny, if there is any mythology, it’s kind of conflated with Beatrix Potter or Peter Cottontail. It’s this foggy, hazy thing,” says Peter Ramsey, director of Rise of the Guardians. “I don’t know if anyone has done anything [definitive] on the Tooth Fairy besides The Rock being in a movie about her.”

In that regard, Ramsey knows this movie has a responsibility to the characters, since it could so easily shape the way kids view them. “When I first came on, I think right off the bat, my instinct – along with everyone else’s – was not to do this as any parody or spoof,” he said. “These are beings who are real to a majority of the audience, or were at one point or another. We thought, ‘Let’s take belief seriously.’”

If Rise of the Guardians adds anything to the existing mythology, Ramsey hopes it’s that Santa, the Easter Bunny, and the Tooth Fairy are not just generous gift-givers, but also strong, selfless, and – above all – brave.

“They don’t have a warlike side,” he says, though they’re certainly tougher than other images of the characters. “Their whole existence is based on the idea that a full, rich, loving, adventurous life for a kid is worth anything they would possibly have to sacrifice. That’s the idea of being a Guardian. It’s kind of analogous to being a good parent, really.”

Here’s a gallery of each of the main characters, along with details from Joyce and Ramsey about their bizarre and colorful histories.